钵苗在鸭嘴式栽植机构中的运动微分方程及应用试验

随着机械化栽植速度的提高,为避免在栽植过程中,钵苗在栽植机构的栽植嘴内运动时间过长而无法及时落入苗沟或穴坑造成栽植失败,并对下一循环的栽植产生不利影响,该文将钵苗相对栽植嘴的运动分为与栽植嘴壁面碰撞、平面运动和沿栽植嘴壁面下滑3个阶段,分别建立了各阶段钵苗的运动微分方程。选择穴盘规格为128孔、苗龄为2~3片真叶、土钵含水率63%左右的西兰花钵苗,利用所建立的钵苗运动微分方程计算得到了变形椭圆齿轮行星轮系栽植机构作业时钵苗与栽植嘴之间的相对运动、相互作用力和钵苗从进入到离开栽植嘴的时间。利用高速摄影及其视频处理技术对钵苗在变形椭圆齿轮行星轮系栽植机构栽植嘴中的运动进行了试验研究,得到的钵苗从进入到离开栽植嘴时间与理论分析基本吻合,可见模型的建立及其计算是正确的。同时分析得到当投苗时钵苗轴线与水平面夹角为55°、质心速度为1.5 m/s、质心速度与水平面夹角为68°时,此栽植机构在速度小于147 r/min时钵苗能顺利落入穴坑,为栽植机构的最高转速设计提供了依据。

Motion differential equations of seedling in duckbilled planting nozzle and its application experiment

Abstract: During the operation of planting mechanism with duckbilled planting nozzle, seedlings fall into ditch or hole under the action of gravity after they are thrown into the planting nozzle, then the transplanter carries out earthing and tamp. The planting nozzle is to keep the seedling upright during the process of dropping and to make the placement accurate. The seedling is free during the entire process so it is not easy to be damaged. During the process, the friction between seedling and planting nozzle affects the drop time. Especially, with the increase of planting velocity, sometimes the seeding's movement time in planting nozzle is too long, so that seedling can't fall into ditch or hole in time, and it causes planting failure, which also has adverse effect on the next planting cycle. In order to avoid this situation, in this paper, the movement of seedling relative to planting nozzle was divided into three stages. The first stage is that seedling falls into the planting nozzle and crashes with the planting nozzle. This collision can be defined as plastic collision form the mechanical property of seedling. The second stage is that seedling does planar motion after collision. During this stage, seedling slides along the planting nozzle and spins along the collision point at the same time. The third stage is that seedling slides along the planting nozzle. During this process, the movement of seedling relative to planting nozzle can be regarded as the linear acceleration movement. This paper established differential equations for each stage. In order to verify the validity of the model, in this paper, 128-hole-plate was used, and broccoli seedling with 2-3 leaves and 63% water content was chosen as working object, and planting mechanism with planetary deformed elliptic gears was used as carrier, and analysis was conducted. Relative movement and interaction force between seedling and planting nozzle and seeding's movement time in planting nozzle were got from the analysis. The movement of seedling in planting nozzle was also studied by using high-speed camera and video processing technology. The measured time from seedling entering the planting nozzle to seedling leaving the planting nozzle basically agrees well with the calculated time. It shows that the differential equations and the calculation are correct. The analysis and experiment also show that the seedling can fall into the hole successfully, when the seedling is thrown into the planting nozzle with the angle of 55° between axis of seedling and horizontal plane, and velocity of seedling's barycenter is 1.5 m/s, and the angle between velocity direction of seedling's barycenter and horizontal plane is 68°, and the velocity of this planting mechanism is less than 147 r/min. This provides design consideration of the maximum speed for planting mechanism.